[hpsdr] Multi-Rx operation w/Alex

[Joe Martin K5SO]

Hi Rod, 

When using Hermes (or a single Mercury) with multiple receivers operating the Alex filters are switched according to whether you have selected automatic Alex switching or manual Alex switching. 

 If in automatic mode, the HPFs (the filters on the Rx Alex fliter board) are switched to the high pass filter appropriate for the lowest frequency of the multiple receivers and the LPFs (the filters on the Tx Alex filter board) are switched to the low pass filter appropriate for highest frequency being used by the multiple receivers, except on transmit in which case the LPFs are switched to the filter appropriate for the transmit frequency.  

This arrangement allows all bands that are being used by the multiple receivers to pass through Alex, automatically.  

In manual Alex switching mode the filters are switched according to how you have set the frequency limits on the manual Alex setup menu.  

If your Alex filters are not switching in this manner then further examination is indicated to determine why not. 

73,  Joe K5SO

On Dec 1, 2012, at 10:42 AM, Rod Brink wrote:

> ***** High Performance Software Defined Radio Discussion List *****
> 
> I got to wondering how Hermes (or Mercury) would behave when Alex is used and multiple Rx operation is invoked.  In Rx the antenna signal is routed first through the Tx LPFs and then through the Rx bandpass filters.  So the question is: if each receiver is tuned to a different band, which set of filters is selected? 
> 
> I ran a little test.  I don't have the Rx bandpass filters, only the Tx LPFs but am certain the behavior is the same.  What seems to happen is that initially the filter corresponding to VFO A is selected.  When the cursor is moved to a different band on the panadaptor and the frequency is changed the filters are instantly switched to that band. 
> 
> Under these conditions signals on all receivers cannot be simultaneously seen on the panadaptor.  They would be were it not for Alex's bandpass filters getting in the way. 
> 
> Isn't the whole purpose of multiple Rx operation to give contestors a view of signals simultaneously occurring on multiple bands...?
> 
> 73,
> 
> Rod, KQ6F
> 
>  
> 
>  
> 
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